A large number of medicament delivery devices such as e.g. injectors have been developed during a number of years, having a number of different features that can facilitate in particular the self-administration of medicament. The features include mixing, priming, penetration, injection, retraction of the injection needle and covering of the injection needle, where all or some of the features are performed automatically upon actuation. These features have been combined in many ways in different injectors.
A main design of the above mentioned type of injectors is a generally elongated tubular shape as well as a pen-shape. The advantage with this shape is that it can accommodate elongated plunger rods that act on medicament containers, where the plunger rods are acted upon by spiral springs, such that the components are placed after each other in the longitudinal direction of the injector.
However, this design also means that the injector tends to be rather long, and in particular when a number of the above mentioned features are included in the injector. This can be a major drawback for the users and in particular when the injectors are used publicly and/or if the user has to carry the injector with him. Most users do not want to show others that they use such medicament delivery devices, and therefore there is a general desire that they are as small as possible.
Document U.S. Pat. No. 5,137,516 discloses an injection device that is divided in two parts when not in use, which parts are stored in a housing, which fits into the pocket or handbag of the user. When the injector is to be used, the housing is opened; a syringe administrating device is pulled out and threaded onto a syringe cartridge housing containing a medicament container onto which an injection needle is attached. When threaded together the assembled injector is withdrawn from the housing whereby a rubber septum covering the needle is removed. The injector is now ready for use. The housing could further include compartments for further syringe cartridge housings.
The major drawback with the solution according to U.S. Pat. No. 5,137,516 is that when the injector is ready for use, it is as long as any ordinary injector with plunger rod and injection spring acting on the plunger rod. It is thus not really discrete when it is used, which is a drawback, according to a number of users who do not want to display their devices.